This invention was made with Government support under contract DE-AC05-840R21400 to Lockheed Martin Energy Systems, Inc. and the Government has certain rights in this invention.
The present invention relates to a method of bonding glass components at temperatures below 100xc2x0 C., and more specifically, to a method of bonding two mating pieces of material together using a monomolecular or quasi-molecular film that covalently bonds to both surfaces.
Low temperature bonding methods can enable technology by allowing the manufacture of devices that include a broader range of materials. Temperature processing can limit materials selection due to decomposition, vaporization, dissolution, or coefficient of expansion. For example, a variety of micro devices for chemical and biochemical analysis are being developed.
The fabrication of many of these devices requires the bonding of glass components, such as the bonding of a glass cover plate to a photo lithographically etched glass substrate, in order to produce a device containing closed micro channels. This bonding process has previously been carried out by fusing the two components at high temperature (e.g. 500-1,100xc2x0 C.), preventing the inclusion of bio-molecules or other temperature-sensitive materials in open channels. It also allows the two components to have different thermal coefficients of expansion.
Currently under development are devices for the analysis of nucleic acids. These devices require the attachment of nucleic acid probes to specific sites within the micro channels formed in a glass substrate, which is most efficiently carried out in open channels prior to bonding a cover plate to the substrate. However, conventional, high temperature bonding techniques would damage the probes and thus compromise the integrity of the analysis. Moreover, adhesive bonding techniques are undesirable given the very small (micron order) dimensions of the micro channels.
Thus, a continuing need exists for a low temperature bonding technique.
An object of the present invention is to provide a low temperature bonding process that will allow the incorporation of DNA probes or other temperature-sensitive molecules on the substrates and facilitate manufacture of such devices.
Another object of the present invention is to provide a method of bonding two different types of glass substrate materials together or the inclusion of thin metal films on a structure prior to bonding. In the former case, high temperatures preclude bonding due to different coefficients of thermal expansion. After bonding at high temperature, stress is introduced by the variation in dimension upon cooling to room temperature.
Another object of the present invention is to provide a low temperature bonding technique that obviates problems associated with metal films which are deposited at high temperatures, by avoiding vaporization or diffusion into the substrate material.
These and other objects are achieved by providing a method of bonding two mating pieces of material together which includes applying an aqueous solution of sodium silicate to a surface of one of the two mating pieces, and then contacting the mating pieces with the aqueous solution therebetween.
Preferably, the solution is spun-on at high speed on the one piece, and then the other piece is immediately brought into contact.
Other objects, advantages, and salient features of the invention will become apparent from the following detailed description, which taken in with the annexed drawings, discloses the preferred embodiment of the present invention.